1. Field of the Invention
The invention relates to measuring the restraining pressures that a compressive orthosis serves to apply on a portion of the body.
2. Discussion of Prior Art
The invention is more particularly described for the case where the portion of the body in question is the leg and the compressive orthosis is an elastic stocking. Nevertheless, the invention is not limited to that particular case and it applies to other types of orthosis and/or to other portions of the body, for example elastic strips for application to the leg or to a portion of the leg, a belt for applying pressure to the abdomen, etc.
The pressures exerted by such orthoses are small, of the order of 0 to 100 hPa, and typically of the order of 20 hPa to 70 hPa, in relative pressure terms.
Numerous factors can influence the value of this pressure and can give rise to differences from a standard nominal value, e.g. knitting machine adjustments, manufacturing tolerances, processing such as dying the stockings, etc.
It is therefore necessary to be able to measure accurately and reproducibly the pressure that is really applied by a given compressive orthosis, in particular to verify that complies with nominal values (quality control during manufacture).
Until now, such measurement has been performed by placing the stocking that is to be inspected on a wooden jig or xe2x80x9ctreexe2x80x9d of standardized shape and dimensions (xe2x80x9cHohenstein modelxe2x80x9d, sizes 1, 2, 3, or 4), and by sliding a thin rubber capsule between the stocking and the tree, which capsule constitutes a pressure sensor (a device known as a xe2x80x9cCompritestxe2x80x9d), and by noting the pressure given by the capsule, firstly without the stocking, and then with the stocking. The desired value is obtained by taking the difference between those two values.
Nevertheless, that method suffers from three major drawbacks:
firstly, its accuracy is poor given that firstly the pressure applied by the stocking is relatively small compared with the sensitivity of the pressure gauge capsule, and secondly because placing the sensor between the stocking and the tree changes the tension of the stocking specifically at the location where the measurement is being performed, thus falsifying the measurement;
measurement is difficult and highly dependent on the skill of the operator since it is necessary to slide the capsule between the stocking and the tree while moving the stocking as little as possible: it is thus difficult to ensure that the method is reproducible; and
finally, that method gives local measurements only and in order to obtain another measurement point it is necessary to repeat the operation (putting the capsule into place) as many times as there are desired measurement points.
An object of the invention is to remedy those drawbacks, by proposing a device that makes it possible to draw up a genuine map of the pressures that can be applied by a compressive orthosis on a portion of the body, and having the following advantages:
the measurement is accurate;
the measurement is faithful in that it provides data in a manner that is reproducible and independent of the skill of an operator;
measurements are performed on a large number of points simultaneously (or quasi-simultaneously if multiplexing is used, for example), thereby obtaining an anatomically representative grid for the map of pressures applied by the compressive orthosis;
it can be implemented simply and quickly; and
the various data measurements taken can be digitized, stored, processed, and displayed, in particular for the purpose of interfacing with computer processing.
To this end, the device of the invention which presents a rigid former reproducing the volume of the portion of the body under investigation and suitable for receiving the compressive orthosis is characterized in that the former incorporates a plurality of sensors distributed over different points of the former and configured in such a manner as to avoid significantly modifying the surface profile thereof, and in that said sensors essentially measure the pressure that is applied locally to the former by the orthosis at the location of the sensor and perpendicularly to the surface of the former.
According to a certain number of advantageous features:
the sensors comprise, at each measurement point, a thin wall capable of being subjected to microdeformation under the effect of the pressure applied by the orthosis, and measurement means, in particular a temperature- compensated strain gauge bridge, for measuring said microdeformation;
the thin wall forms a portion of a support pellet fitted to the former in such a manner that its outside surface, which includes the thin wall, is flush with the surface of the former;
the device further comprises means for calibrating the sensors by means of a leakproof enclosure that can be pressurized and that encloses the former; and
the device further comprises means for processing and displaying the measurements taken by the sensors.